The cap normally comprises a plug movable between an open position and a closed position for opening and closing the second end respectively; and an elastically deformable collar fitted to the conduit and connected to the plug by a flexible element to keep the plug and collar connected to each other when the plug is in the open position.
Known infusion and/or withdrawal fittings of the type described above have several drawbacks, mainly due to assembly of the collar to the conduit being relatively complicated, by requiring elastic deformation of the collar by the user.
A further drawback of known infusion and/or withdrawal fittings of the type described above lies in the relative ease with which the collar works loose from the conduit.